Camera and photographic lens

ABSTRACT

A camera is provided which is adapted to receive a photographic lens having a diaphragm. The camera includes a detection unit configured to execute electric charge accumulation for detecting a defocus amount when the diaphragm is in a state having a first aperture value, and a controller configured to, when causing the diaphragm to perform an aperture reducing operation from the first aperture value to a second aperture value, cause the diaphragm to start the aperture reducing operation without waiting for completion of the electric charge accumulation for detecting the defocus amount by the detection unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 12/028,231, filed Feb. 8, 2008, entitled “CAMERA AND PHOTOGRAPHICLENS”, the content of which is expressly incorporated by referenceherein in its entirety. Further, the present application claims priorityfrom Japanese Patent Application No. 2007-038486, filed Feb. 19, 2007,which is also hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a camera configured to detect a defocusamount, a photographic lens mountable on the camera, and a camerasystem.

2. Description of the Related Art

Conventionally, in a camera system, such as an interchangeable lens typesingle-lens reflex camera, an automatic exposure (hereinafter referredto as AE) device has widely been known. The AE device photo-electricallyconverts an object image from a photographic lens to determine anexposure amount (exposure value).

Further, a technique of automatic focus adjustment (hereinafter alsoreferred to as AF) has been known. The AF technique forms images offluxes of light from an object passing through different exit pupilareas of a photographic lens on a pair of line sensors to determine theamount of deviation of the images. The amount of deviation of the imagesis a relative position displacement amount of a pair of image signalsobtained by photo-electrically converting an object image. Then, the AFtechnique detects a defocus amount of the photographic lens with respectto the object based on the amount of deviation of images. Then, the AFtechnique drives the photographic lens based on the detected defocusamount. Further, the AF technique can include a servo mode that causeslens driving to track not only a still object but also a moving object,and can allow continuous shooting.

In a single-lens reflex camera, a factor that determines a speed of thecontinuous shooting includes a time period required for AE and AF and atime period required for a series of photographing operations(hereinafter referred to as a release sequence) from retraction of amirror and driving of shutter to return of the mirror on the camera(main body) side. On the interchangeable lens side, the factor includesa time period required for a diaphragm driving sequence from reducing anaperture of a diaphragm to provide a predetermined exposure to openingthe diaphragm up to a full-aperture position after completion ofexposure.

Further, in a camera system, such as a single-lens reflex camera, atechnique in which a camera obtains a time period required for driving adiaphragm of an interchangeable photographic lens is discussed inJapanese Patent Application Laid-Open No. 10-260449. According toJapanese Patent Application Laid-Open No. 10-260449, the technique iseffective at enabling quick control of a camera system since a lens,which can communicate with a camera during driving of a diaphragm of thelens, can transmit a time period required for driving the diaphragm tothe camera. However, Japanese Patent Application Laid-Open No. 10-260449does not discuss more specific examples.

In order to enhance a continuous shooting performance, the camera systemgenerally executes the release sequence on the camera side and thediaphragm driving sequence on the interchangeable photographic lens sidein parallel. However, a conventional camera system causes a standby timeon the camera side when an aperture reducing time on the photographiclens side is longer than a release sequence time on the camera side.This is remarkable during continuous shooting. This may reduce a speedof continuous shooting.

SUMMARY OF THE INVENTION

The present invention is directed to a camera and a photographic lenswith a technique of allowing execution of higher-speed continuousshooting.

According to an aspect of the present invention, a camera is providedwhich is adapted to receive a photographic lens having a diaphragm. Thecamera includes a detection unit configured to execute electric chargeaccumulation for detecting a defocus amount when the diaphragm is in astate having a first aperture value, and a controller configured to,when causing the diaphragm to perform an aperture reducing operationfrom the first aperture value to a second aperture value, cause thediaphragm to start the aperture reducing operation without waiting forcompletion of the electric charge accumulation for detecting the defocusamount by the detection unit.

According to another aspect of the present invention, a camera isprovided which is adapted to receive a photographic lens having adiaphragm. The camera includes a detection unit configured to executeelectric charge accumulation for detecting a defocus amount when thediaphragm is in a state having a first aperture value, and a controllerconfigured to, when causing the diaphragm to perform an aperture openingoperation from a second aperture value to the first aperture value,cause the detection unit to start the electric charge accumulationwithout waiting for completion of the aperture opening operation.

According to yet another aspect of the present invention, a photographiclens includes a diaphragm unit configured to adjust an amount of lightof an object light flux to be directed to an image pickup unit of acamera on which the photographic lens is mounted, and a diaphragmdriving time prediction unit configured to output, to the camera,information on a predicted time period for which the diaphragm unit doesnot block the object light flux after the diaphragm unit starts anaperture reducing operation from a first aperture value to a secondaperture value.

According to an exemplary embodiment of the present invention, atechnique is provided which allows execution of higher-speed continuousshooting.

Further features and aspects of the present invention will becomeapparent from the following detailed description of exemplaryembodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate exemplary embodiments, features,and aspects of the invention and, together with the description, serveto explain the principles of the invention.

FIG. 1 is a diagram illustrating an exemplary configuration of asingle-lens reflex camera system according to an exemplary embodiment ofthe present invention.

FIGS. 2A and 2B are diagrams illustrating an example release sequence ona camera side and an example diaphragm driving sequence on aphotographic lens side, respectively, during continuous shootingaccording to an exemplary embodiment of the present invention.

FIG. 3 is a flowchart illustrating an example operation of a cameraaccording to an exemplary embodiment of the present invention.

FIG. 4 is a flowchart illustrating a photographing operation to beexecuted in step S109 in FIG. 3.

FIGS. 5A and 5B are diagrams illustrating an example release sequence ona camera side and an example diaphragm driving sequence on aphotographic lens side, respectively, during continuous shootingaccording to a conventional single-lens reflex camera.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Various exemplary embodiments, features, and aspects of the inventionwill be described in detail below with reference to the drawings.

FIG. 1 is a diagram illustrating an exemplary configuration of aninterchangeable lens type single-lens reflex camera system, whichincludes a photographic lens 100 and a camera 200, according to anexemplary embodiment of the present invention. In FIG. 1, thephotographic lens 100 includes a lens micro processing unit (MPU) 1 anda lens position output unit 2 configured to detect an image formingposition of a lens 14. The photographic lens 100 further includes a lensdriving unit 3 configured to drive the lens 14 and a diaphragm drivingunit 4 configured to drive a diaphragm 15.

The lens position output unit 2 outputs, to the camera 200, a relativeposition of the lens 14 as a pulse signal for the lens driving unit 3.The lens 14 includes an image forming function. Accordingly, the lensposition output unit 2 measures information corresponding to an imageforming position of the photographic lens 100 and outputs theinformation to the camera 200. More specifically, an encoder of the lensposition output unit 2 outputs an optical change in a movable lens unitas a change in electric potential. The lens MPU 1 counts the change inelectric potential to measure the information.

The lens MPU 1 includes tables 5 and 6. The table 5 stores a predicteddiaphragm driving time (predicted aperture reducing time) required whenthe diaphragm 15 executes an aperture reducing operation. In the contextof the present specification, the term “aperture reducing operation”refers to an operation for reducing an aperture value of the diaphragm15 from a first aperture value that corresponds to a full-apertureposition to a second aperture value that corresponds to an aperturevalue set by a user or a camera MPU 9. In the table 5, the lens MPU 1searches for a predicted aperture reducing time based on an aperturevalue that is set by the user or the camera MPU 9. The table 6 stores apredicted diaphragm driving time (predicted aperture opening time)required when the diaphragm 15 executes an aperture opening operationfrom a reduced-aperture position to the full-aperture position. In thetable 6, the lens MPU 1 searches for a predicted aperture opening timebased on the set aperture value.

Additionally, the predicted aperture reducing time includes entrancetime and actual aperture reducing time, which are separately stored inthe table 5. The predicted aperture opening time includes actualaperture opening time and retraction time, which are separately storedin the table 6. The lens MPU 1 can communicate with the camera MPU 9 viaa mount 16. Thus, the lens MPU 1 can transmit information on time storedin the tables 5 and 6 to the camera MPU 9. More specifically, thediaphragm 15 of the photographic lens 100 is designed with the stoppingaccuracy of movable blades of the diaphragm 15 and the fluctuation ofthe blades when the aperture of the diaphragm 15 is fully opened.Accordingly, when the diaphragm 15 reduces the aperture from thefull-aperture position, the diaphragm 15 includes an area in whichobject light is not blocked by the blades of the diaphragm 15 (area inwhich at least a part of an object light flux is not blocked by thediaphragm 15). This area is referred to as a retraction area.

FIG. 2A is a timing chart illustrating a release sequence on the cameraside. FIG. 2B is a timing chart illustrating a diaphragm drivingsequence on the photographic lens 100 side. In FIG. 2B, a solid line Aindicates opening and closing driving of the blades of the diaphragm 15.

Thus, during the aperture reducing operation of the diaphragm 15 and theaperture opening operation of the diaphragm 15, when the diaphragmblades (solid line A in FIG. 2) exist in the retraction area, the amountof light to be directed to an image pickup plane and a finder 22 doesnot change. That is, at the time of entrance and retraction of thediaphragm blades to be executed in the retraction area, AF and AE can beexecuted. In other words, in a predicted diaphragm driving time from afull-aperture position or a reduced-aperture position of the diaphragm15 for which the amount of light for shooting is not influenced by thediaphragm 15, AF and AE can be executed. This is because the predicteddiaphragm driving time is a predicted time period for which thediaphragm 15 does not block an object light flux after starting theaperture reducing operation or the diaphragm 15 does not block an objectlight flux after starting the aperture opening operation.

FIGS. 5A and 5B are diagrams to be compared with FIGS. 2A and 2B. FIG.5A, which corresponds to FIG. 2A, is a timing chart illustrating arelease sequence on the camera 200 side. FIG. 5B, which corresponds toFIG. 2B, is a timing chart illustrating a diaphragm driving sequence onthe photographic lens 100 side. In FIG. 5B, similarly to FIG. 2B, asolid line A indicates opening and closing driving of the diaphragmblades. As illustrated in FIGS. 5A and 5B, as compared with FIGS. 2A and2B, if the aperture reducing operation of the diaphragm 15 is startedafter waiting for completion of AE/AF, a waiting time occurs on thecamera 200 side. Further, if the AE/AF operation is started afterwaiting for completion of the aperture opening operation of thediaphragm 15, a waiting time occurs on the camera 200 side. This mayparticularly reduce a speed of continuous shooting.

Now referring back to FIG. 1, the interchangeable photographic lens 100includes the above-described lens MPU 1, lens position output unit 2,lens driving unit 3, diaphragm driving unit 4, table 5, and table 6. Theinterchangeable photographic lens 100 is connected to the camera 200(main body) via the mount 16, as shown by broken lines in FIG. 1. Thus,the interchangeable photographic lens 100 is detachably mounted on thecamera (main body) 200.

The camera 200 includes alight metering unit 7. The light metering unit7 photo-electrically converts an object image received via a lightmetering optical system (not illustrated) into a change in electricpotential. A detection unit 8 is configured to detect a defocus amountby photo-electrically converting an object image received via asecondary image-forming optical system (not illustrated) to executeelectric charge accumulation. The detection unit 8 outputs storedelectric charge as a change in electric potential. The camera MPU 9 canmutually communicate with the lens MPU 1 via signal lines of the mount16. Further, the camera MPU 9 contains an analog-to-digital (A/D)conversion unit (not illustrated). Furthermore, the camera MPU 9contains a timer (not illustrated). The timer can measure time and atime period.

The camera 200 further includes a dial unit 10 configured to definevarious settings (shutter speed, aperture value, photographing mode,etc.) of the camera 200 and an image pickup unit 11. An exposure unit 12executes retraction and return of a main mirror 17 and a sub mirror 18and shutter control of an image pickup plane under the control of thecamera MPU 9. A switch SW1 is turned on by a first stroke operation(half press) on the release button. A switch SW2 is turned on by asecond stroke operation (full press) on the release button.

In addition, the camera 200 includes an image sensor 19, a focusingscreen 20, a pentagonal mirror 21, and a finder 22.

The camera MPU 9 executes a light metering calculation required forautomatic exposure based on an output from the light metering unit 7.More specifically, an object image reflected from the main mirror 17 andformed on the focusing screen 20 is directed to the light metering unit7 via the light metering optical system (not illustrated). The lightmetering unit 7 includes a photoelectric conversion element. The lightmetering unit 7 executes electric charge accumulation for apredetermined time period and outputs luminance of an object as a changein electric potential. The camera MPU 9 reads this signal as a numericalvalue by the A/D conversion unit. The camera MPU 9 performs a lightmetering calculation on the read numerical value. Thus, the camera MPU 9determines exposure corresponding to a photographing mode, such as ashutter priority, an aperture priority, or the like.

The camera MPU 9 calculates a defocus amount, which is an amount offocus deviation required for automatic focus adjustment, based on anoutput from the detection unit 8, which is configured to detect thedefocus amount. More specifically, the camera MPU 9 calculates thedefocus amount based on an image deviation amount of two images formedfrom object light fluxes passing through two different areas interposingan optical axis of the photographic lens 100. The light fluxes of twoimages pass through the main mirror 17, which is a half mirror. Then,the light fluxes are reflected by the sub mirror 18, which is locatedbehind the main mirror 17, and are directed to the detection unit 8 by asecondary image-forming optical system (not illustrated).

The detection unit 8, which is configured to detect a defocus amount,includes a linear photoelectric conversion element. The detection unit 8outputs an object image formed on the photoelectric conversion elementas a change in electric potential. Unlike the light metering unit 7,when the accumulation of electric charge required for focus detection iscompleted, the detection unit 8 automatically terminates electric chargeaccumulation. However, when brightness of an object is low, thedetection unit 8 consumes time for electric charge accumulation. Thus,in order to maintain a speed of shooting during continuous shooting,after a predetermined time has passed, the detection unit 8 forciblyterminates electric charge accumulation and reads an image signal. Thecamera MPU 9 reads signals of such two images as a change in numericalvalue with the A/D conversion unit. The camera MPU 9 applies correlationcalculation to the signals to calculate an image deviation amount of twoimages, thus determining the defocus amount.

Next, an operation of the single-lens reflex camera 200 having theabove-described configuration will be described with reference to aflowchart illustrated in FIG. 3.

In the present embodiment, when the switch SW1 is turned on in stepS101, the camera MPU 9 starts AF and AE operations. First, in step S102,the camera MPU 9 starts electric charge accumulation for a photoelectricconversion element included in the light metering unit 7. In step S103,the camera MPU 9 starts electric charge accumulation for a photoelectricconversion element (defocus amount detection operation) included in thedetection unit 8, which is configured to detect a defocus amount. Then,in next step S104, the camera MPU 9 determines whether electric chargeaccumulation for light metering for a predetermined time is completed.If the electric charge accumulation is not completed (NO in step S104),the processing waits until the completion of the electric chargeaccumulation. If the electric charge accumulation is completed (YES instep S104), the processing proceeds to step S105. In step S105, thecamera MPU 9 executes the above-described light metering calculation.

When the light metering calculation is completed in step S105, theprocessing proceeds to step S106. In step S106, the camera MPU 9determines whether the switch SW2 is turned on. If the switch SW2 isturned on (YES in step S106), the processing proceeds to step S109. Instep S109, the camera MPU 9 executes a series of photographingoperations (details will be described later). Then, the processingproceeds to step S110. On the other hand, if the switch SW2 is notturned on (NO in step S106), the processing proceeds to step S107. Instep S107, the camera MPU 9 determines whether electric chargeaccumulation for a photoelectric conversion element included in thedetection unit 8, which is configured to detect a defocus amount, iscompleted. If the electric charge accumulation is not completed (NO instep S107), the processing waits until the completion of the electriccharge accumulation. Thereafter, when the electric charge accumulationis completed (YES in step S107), the processing proceeds to step S108.In step S108, the camera MPU 9 executes the above-described calculationof a defocus amount. Then, the processing proceeds to step S110. In stepS110, the camera MPU 9 controls the lens driving unit 3 to drive thelens 14, that is, to perform focus adjustment, based on the calculateddefocus amount.

After the above-described driving of the lens 14 is completed, theprocessing proceeds to step S111. In step S111, the camera MPU 9determines whether the switch SW1 is turned on. If the switch SW1 isturned on (YES in step S111), the processing returns to a start of lightmetering in step S102. Hereafter, the camera MPU 9 repeats the flow ofAF and AE until the switch SW1 is turned off in step S112.

Next, a photographing operation to be executed in step S109 in FIG. 3will be described with reference to a flowchart illustrated in FIG. 4.

The camera MPU 9 starts an operation in step S201. First, in step S202,the camera MPU 9 transmits an aperture value determined in step S105from the camera 200 to the photographic lens 100. Then, the camera MPU 9acquires, from the photographic lens 100, a predicted time periodrequired for driving the diaphragm 15 corresponding to the aperturevalue (predicted diaphragm driving time). That is, the camera MPU 9acquires four values of entrance time, actual aperture reducing time,actual aperture opening time, and retraction time (see FIG. 2B) from thephotographic lens 100 (in detail, tables 5 and 6). Note that, asdescribed above, the entrance time refers to a predicted time period forwhich the diaphragm 15 does not block an object light flux afterstarting an aperture reducing operation. Further, the retraction timerefers to a predicted time period for which the diaphragm 15 does notblock an object light flux after starting an aperture opening operation.

After the camera MPU 9 completes acquisition of the predicted diaphragmdriving time, the processing proceeds to step S203. In step S203, thecamera MPU 9 determines whether electric charge accumulation for thephotoelectric conversion element included in the detection unit 8, whichis configured to detect a defocus amount, is completed. If the electriccharge accumulation is completed (YES in step S203), the processingproceeds to step S208. In step S208, the camera MPU 9 executes theabove-described calculation of a defocus amount. Then, the processingproceeds to step S209. In step S209, the camera MPU 9 starts an aperturereducing operation from a full-aperture state, as a first aperturevalue, to provide an aperture value, as a second aperture value,determined in step S105 in FIG. 3. Then, the processing proceeds to stepS210.

On the other hand, if the camera MPU 9 determines that the electriccharge accumulation for the photoelectric conversion element included inthe detection unit 8, which is configured to detect a defocus amount, isnot completed (NO in step S203), the processing proceeds to step S204.Then, in step S204, the camera MPU 9 determines whether a time obtainedby subtracting entrance time from electric charge accumulation timepredetermined to detect a defocus amount in order to maintain a speed ofcontinuous shooting is positive. If the time is positive (YES in stepS204), a time for continuing the electric charge accumulation stillremains. Thus, the processing returns step S203. Thereafter, the cameraMPU 9 executes similar operations. If the time is negative or zero (NOin step S204), the processing proceeds to step S205. In step S205, thecamera MPU 9 starts an aperture reducing operation. At this time, thecamera MPU 9 executes the electric charge accumulation for thephotoelectric conversion element for detecting a defocus amount inparallel with the entrance time of the diaphragm 15. That is, when thecamera MPU 9 executes the aperture reducing operation from the firstaperture value to the second aperture value of the diaphragm 15, thecamera MPU 9 starts the aperture reducing operation without waiting forcompletion of the electric charge accumulation for detecting a defocusamount. As illustrated in FIG. 2B, even if the diaphragm 15 operateswithin the entrance time in the retraction area, the diaphragm 15 doesnot block an object light flux. Thus, the amount of light does notchange. Accordingly, this allows the electric charge accumulation fordetecting a defocus amount.

Note that AE, among AE/AF illustrated in FIG. 2A, corresponds to thestart of light metering in step S102, the electric charge accumulationfor light metering in step S104, and the light metering calculation instep S105 in FIG. 3. Further, AF corresponds to the start of thedetection operation of a defocus amount in step S103 in FIG. 3, that is,the start of the electric charge accumulation for detecting a defocusamount, the electric charge accumulation for detecting a defocus amountin step S203, the calculation of a defocus amount in step S207, and thecalculation of a defocus amount in step S208 in FIG. 4.

After the camera MPU 9 starts the aperture reducing operation, theprocessing proceeds to step S206. In step S206, the camera MPU 9determines whether the electric charge accumulation for detecting adefocus amount reaches time for discontinuation. If the electric chargeaccumulation for detecting a defocus amount does not reach the time fordiscontinuation (NO in step S206), the processing waits in this stepuntil it reaches the time for discontinuation. Thereafter, if the cameraMPU 9 determines that it reaches the time for discontinuation (YES instep S206), the processing proceeds to step S207. In step S207, thecamera MPU 9 forcibly terminates the electric charge accumulation andexecutes calculation of a defocus amount.

After the camera MPU 9 starts the calculation of a defocus amount instep S207 or the aperture reducing operation in step S209, theprocessing proceeds to step S210. In step S210, the camera MPU 9executes driving of the lens 14 based on the calculated defocus amount.Thereafter, the processing proceeds to step S211. In step S211, thecamera MPU 9 starts retraction of the mirrors 17 and 18 from an objectlight path with the exposure unit 12. Then, in step S212, the camera MPU9 determines whether the retraction of the mirrors 17 and 18 from theobject light path is completed. If the camera MPU 9 determines that theretraction of the mirrors 17 and 18 is completed (YES in step S212), theprocessing proceeds to step S213. In step S213, the camera MPU 9determines whether the aperture reducing operation is completed. If theaperture reducing operation is completed (YES in step S213), theprocessing proceeds to step S214. In step S214, the camera MPU 9executes exposure of the image sensor 19 to record and store an objectimage.

Thereafter, the processing proceeds to step S215. In step S215, thecamera MPU 9 starts return of the mirrors 17 and 18 with the exposureunit 12. Then, in step S216, the camera MPU 9 starts an aperture openingoperation of the diaphragm 15 from a set aperture value to afull-aperture state. In step S217, the camera MPU 9 determines whetherthe return of the mirrors 17 and 18 is completed. If the return of themirrors 17 and 18 is completed (YES in step S217), the processingproceeds to step S218. In step S218, the camera MPU 9 determines whetherAE and AF can be started. More specifically, the camera MPU 9 determineswhether a time period from the start of an aperture opening operation toan actual full-aperture position to fully open the diaphragm 15 haspassed. That is, until the actual full-aperture position, the diaphragm15 blocks at least a part of an object light flux. The camera MPU 9determines whether a time period for which at least a part of an objectlight flux is blocked has passed. If the camera MPU 9 determines thatthe time has passed, that is, determines that AE and AF can be started(YES in step S218), the processing proceeds to step S219. Then, theprocessing returns to step S109 in FIG. 3. This allows the camera MPU 9to detect a defocus amount in parallel with retraction time of thediaphragm 15 during continuous shooting. That is, during the apertureopening operation from an aperture value set as the second aperturevalue of the diaphragm 15 to a full-aperture state as the first aperturevalue thereof, the camera MPU 9 starts electric charge accumulation fordetecting a defocus amount by the detection unit 8 without waiting forcompletion of the aperture opening operation.

Further, an operation performed in parallel with AE will be describedbelow. If the processing returns from step S219 to the flow illustratedin FIG. 3 and the switch SW1 is continuously turned on in step S111, thecamera MPU 9 executes light metering calculation for next shooting insteps S102, S104, and S105. The camera MPU 9 executes the light meteringcalculation in parallel with the retraction time of the diaphragm 15 asillustrated in FIGS. 2A and 2B.

In the above-described configuration, the photographic lens 100 outputs,to the camera 200, a predicted aperture reducing time (entrance time andactual aperture reducing time) and a predicted aperture opening time(actual aperture opening time from a predetermined aperture value to afull aperture value and retraction time) illustrated in FIG. 2B. Then,the entrance time is set as an AF operable time (defocus amountdetectable time). The actual aperture reducing time is set as an AFinoperable time (defocus amount undetectable time). Further, the actualaperture opening time is set as an AE inoperable time (light meteringcalculation inoperable time) and an AF inoperable time. The retractiontime is set as an AE operable time (light metering calculation operabletime) and an AF operable time.

A single-lens reflex camera allowing higher-speed continuous shootingcan be provided by outputting the AF and AE operable time (entrance timeand retraction time) from the photographic lens 100 to the camera 200and executing AF and AE in parallel with the diaphragm driving operationbased on the AF and AE operable time.

In the present exemplary embodiment, the entrance time and theretraction time are set as an AF operable time. The actual aperturereducing time and the actual aperture opening time are set as an AFinoperable time. However, in the case of an AF system that needs only alight flux of a predetermined aperture value, for example, F5.6,irrespective of a full-aperture F value of a photographic lens, if theset aperture value is up to F5.6, all of the diaphragm driving time upto F5.6 can be set as an AF operable time irrespective of the aperturereducing state. Further, if the set aperture value is larger than F5.6,the diaphragm driving time until the aperture is reduced to F5.6 can beset an AF operable time, and the diaphragm driving time thereafter canbe set as an AF inoperable time.

Similarly, if the aperture of the diaphragm 15 is opened from a statewhere the aperture is reduced up to F5.6, all of the diaphragm drivingtime up to F5.6 can be set as an AF operable time irrespective of theaperture opening state. Further, if the aperture of the diaphragm 15 isopened from a state where the aperture is reduced from a value largerthan F5.6, the diaphragm driving time until the aperture of thediaphragm 15 is opened to F5.6 can be set as an AF inoperable time, andthe diaphragm driving time thereafter can be set an AF operable time.

In the present exemplary embodiment, the tables 5 and 6 includepremeasured fixed values. The table 5 stores a predicted time requiredto reduce an aperture of the diaphragm 15. The table 6 stores apredicted time required to open an aperture of the diaphragm 15.However, in the case of a camera system in which the diaphragm drivingtime is changed by temperature or aging, the lens MPU 1 can observe itschange and correct the diaphragm driving time. More specifically, thelens MPU 1 can observe temperature to execute a correction or calculatesa difference between the tables 5 and 6 and the actual diaphragm drivingtime, store the difference, and execute a correction of a predicteddiaphragm driving time based on the difference. Alternatively, thecamera MPU 9 can observe temperature, transmits the temperature to thelens MPU 1. Based on the temperature, the lens MPU 1 can correct thepredicted aperture reducing time table 5 and the predicted apertureopening time table 6.

Further, the above-described exemplary embodiment exemplifies asingle-lens reflex camera including a combination of the photographiclens 100 and the camera (main body) 200. However, the present inventioncan also be applied to a lens-integrated camera.

For example, the table 5, which stores a predicted time required toreduce the aperture of the diaphragm 15, and the table 6, which stores apredicted time required to open the aperture of the diaphragm 15, areprovided not in the photographic lens 100 but in the camera 200. Thisenables reducing the amount of communication between the photographiclens 100 and the camera 200. However, such a case may limit theadaptable types of the photographic lens 100 and make the capacity ofthe tables 5 and 6 larger.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications, equivalent structures, and functions.

This application claims priority from Japanese Patent Application No.2007-038486 filed Feb. 19, 2007, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. A camera adapted to receive a photographic lenshaving a diaphragm, the camera comprising: a detection unit configuredto execute electric charge accumulation for detecting a defocus amountwhen the diaphragm is in a state having a first aperture value; and acontroller configured to, when causing the diaphragm to perform anaperture reducing operation from the first aperture value to a secondaperture value, cause the diaphragm to start the aperture reducingoperation without waiting for completion of the electric chargeaccumulation for detecting the defocus amount by the detection unit. 2.The camera according to claim 1, wherein the controller causes thediaphragm to start the aperture reducing operation without waiting forcompletion of the electric charge accumulation for detecting the defocusamount utilizing existence of an area in which the diaphragm does notblock an object light flux when the diaphragm performs the aperturereducing operation from the first aperture value to the second aperturevalue.
 3. The camera according to claim 1, wherein the controlleracquires, from the photographic lens, time information on a predictedtime period for which the diaphragm does not block an object light fluxafter the diaphragm starts the aperture reducing operation, and, basedon the time information, causes the diaphragm to start the aperturereducing operation without waiting for completion of the electric chargeaccumulation for detecting the defocus amount when the diaphragmperforms the aperture reducing operation from the first aperture valueto the second aperture value.
 4. A photographic lens comprising: adiaphragm unit configured to adjust an amount of light of an objectlight flux to be directed to an image pickup unit of a camera on whichthe photographic lens is mounted; and a diaphragm driving timeprediction unit configured to output, to the camera, information on apredicted time period for which the diaphragm unit does not block theobject light flux after the diaphragm unit starts an aperture reducingoperation from a first aperture value to a second aperture value.
 5. Aphotographic lens comprising: a diaphragm unit configured to adjust anamount of light of an object light flux to be directed to an imagepickup unit of a camera on which the photographic lens is mounted; and adiaphragm driving time prediction unit configured to output, to thecamera, information on a predicted time period for which the diaphragmunit does not block the object light flux after the diaphragm unitstarts an aperture opening operation from a second aperture value to afirst aperture value.
 6. A camera system comprising: a camera; and aphotographic lens having a diaphragm, the lens being mountable to thecamera; wherein the camera includes, a detection unit configured toexecute electric charge accumulation for detecting a defocus amount whenthe diaphragm is in a state having a first aperture value; and acontroller configured to, when causing the diaphragm to perform anaperture reducing operation from the first aperture value to a secondaperture value, cause the diaphragm to start the aperture reducingoperation without waiting for completion of the electric chargeaccumulation for detecting the defocus amount by the detection unit; andwherein the photographic includes, a diaphragm unit configured to adjustan amount of light of an object light flux to be directed to an imagepickup unit of a camera on which the photographic lens is mounted; and adiaphragm driving time prediction unit configured to output, to thecamera, information on a predicted time period for which the diaphragmunit does not block the object light flux after the diaphragm unitstarts an aperture reducing operation from a first aperture value to asecond aperture value.
 7. A camera system comprising: a camera; and aphotographic lens having a diaphragm, the lens being mountable to thecamera; wherein the camera includes, a detection unit configured toexecute electric charge accumulation for detecting a defocus amount whenthe diaphragm is in a state having a first aperture value; and acontroller configured to, when causing the diaphragm to perform anaperture reducing operation from the first aperture value to a secondaperture value, cause the diaphragm to start the aperture reducingoperation without waiting for completion of the electric chargeaccumulation for detecting the defocus amount by the detection unit; andwherein the photographic includes, a diaphragm unit configured to adjustan amount of light of an object light flux to be directed to an imagepickup unit of a camera on which the photographic lens is mounted; and adiaphragm driving time prediction unit configured to output, to thecamera, information on a predicted time period for which the diaphragmunit does not block the object light flux after the diaphragm unitstarts an aperture opening operation from a second aperture value to afirst aperture value.